This invention relates generally to coaxial cables, and more particularly to flexible coaxial cables with tape outer conductor layers having surfaces defining a plurality or pattern of indentations.
Coaxial cables have employed several different types of outer conductors. Four types of outer conductors commonly used are as follows:
1) braided wire employed for the outer conductor providing excellent flexibility, but resulting in cables with high attenuation and poor RF shielding at a relatively high cost;
2) flat tape with braid applied over it providing lower attenuation and better RF shielding, but not having as good flexibility as the braided wire outer conductor, and having a slightly higher cost;
3) corrugated copper or aluminum tubes providing excellent shielding and low loss, but being stiff and expensive; and
4) smooth wall copper or aluminum tubes providing the lowest loss and excellent shielding, but being extremely stiff and expensive.
Smooth aluminum or copper tapes such as those commonly applied underneath a braid can be applied without a braid, but the resulting cable is stiff and has a very limited flex life.
It is a general object of the present invention to provide a flexible coaxial cable that avoids the above-mentioned drawbacks.
In a first aspect of the present invention, a flexible coaxial cable includes an inner conductor, and a dielectric layer generally surrounding the inner conductor. A generally flat outer conductor generally surrounds the dielectric layer, and does not underlie another electrically conductive layer such as a braided wire layer. The generally flat outer conductor includes a surface defining a plurality of indentations for minimizing damage to the generally flat outer conductor resulting from bending or repeated flexing of the cable.
In a second aspect of the present invention, a flexible coaxial cable includes an inner conductor, and a dielectric layer generally surrounding the inner conductor. A tape outer conductor generally surrounds the dielectric layer, and does not underlie another electrically conductive layer such as a braided wire layer. The tape outer conductor includes a surface defining a plurality of indentations for minimizing damage to the tape outer conductor resulting from bending or repeated flexing of the cable. The cable may include an insulating jacket generally surrounding the tape outer conductor.
A first advantage of the present invention is that the coaxial cable has an increased flex life relative to a coaxial cable having a smooth-surfaced tape outer conductor.
A second advantage of the present invention is that the coaxial cable has excellent RF shielding.
A third advantage of the present invention is that the coaxial cable is inexpensive relative to a coaxial cable having a braided wire layer.
A fourth advantage of the present invention is that the coaxial cable is smaller in diameter and of lower weight relative to a coaxial cable having a braided wire layer.
A fifth advantage of the present invention is the relatively small diameter cable lends itself to ease of installation